The currently approved antipsychotic drugs share the common feature of reducing the dopamine signalling in the brain. This is achieved through either a dopamine D2 receptor antagonistic or partial agonistic effect. The first generation antipsychotics (also referred to as “typical”) are often associated with extra-pyrimidal side effects wherefore the use of these agents have diminished. Second generation or “atypical” antipsychotics in addition to the D2 receptor affinity have affinity to the serotonin receptor 2A (5-HT2A). Some atypical antipsychotics in addition have affinity for the 5-HT2C, 5-HT6, or 5-HT7 receptors. Atypical antipsychotics give rise to fewer extra-pyrimidal side effects, but are still hampered by weight gain and QTC effects. Examples of atypicals are clozapine, olanzapine and risperidone.
More recently, neurokinin receptors have been suggested as targets for CNS diseases [Albert, Expert Opin. Ther. Patents, 14, 1421-1433, 2004]. Neurokinins (or tachykinins) are a family of neuropeptides, which include substance P(SP), neurokinin A (NKA), and neurokinin B (NKB). The biological effects of these substances are primarily effected through binding to and activation of the three neurokinin receptors NK1, NK2, and NK3. Although some cross reactivity probably exists, SP has the highest affinity and is believed to be the endogenous ligand for NK1, and likewise for NKA and NK2, and for NKB and NK3.
NK3 is primarily expressed centrally in regions including cortical regions, such as frontal, parietal and cingulated cortex; nuclei of the amygdale, such as the basal, central and lateral nuclei; the hippocampus; and mesencephalon structures, such as ventral tegmental area, substantia nigra pars compacta, and dorsal raphe nuclei [Spooren et al, Nature Reviews, 4, 967-975, 2005]. The NK3 receptor is expressed on dopaminergic neurons, and Spooren et al has suggested that the antipsychotic effects of NK3 antagonists are mediated by an inhibition of the dopamine tone, particularly at the D2 receptor combined with a reduction of the serotonergic tone, particularly at the 5-HT2A receptor.
Two structurally distinct NK3 antagonists, namely talnetant and osanetant, have been clinically tested for antipsychotic, and in particular antischizophrenic effects.

Osanetant proved superior to placebo in clinical trials, in particular on positive symptoms of psychosis, i.e. delusions, hallucinations and paranoia [Am. J. Psychiatry, 161, 2004, 975-984]. Similarly, talnetant has been shown in clinical trials to ameliorate the cognitive behaviour of schizophrenics [Curr. Opion. Invest. Drug, 6, 717-721, 2005]. Nevertheless, both compounds are hampered by poor pharmacokinetic and pharmacodynamic properties including poor solubility, poor bioavailability, relatively high clearance, and poor blood-brain barrier penetration [Nature reviews, 4, 967-975, 2005]. These results lend support to the notion that the NK3 receptor is a promising target for the treatment of e.g. psychosis, however emphasising the need for identifying compounds with adequate pharmacokinetic and pharmacodynamic properties.
WO95/32948 discloses a range of quinoline derivatives, including talnetant as NK3 antagonists.
More recently, WO 2006/130080 discloses compounds having the core structure
which compounds are said to be NK3 antagonists; and WO 2006/050991 and WO 2006/050992 disclose further quinolinecarboxamides derivatives, which derivatives are said to be NK3 antagonists.
WO 2005/014575 discloses compounds of the formula
wherein R represents N-containing heterocycles, i.e. pyrazolyl, triazolyl and tetrazolyl.
WO 2008/131779 discloses that isoquinolone derivatives of the formula
are NK3 antagonists.
Finally, Chemistry of Heterocyclic Compounds, Vol. 42 (2), 191-196, 2006 discloses a study on the synthesis of compounds with the following core structure
